Volunteer with a organization serving individuals from a country that speaks the language that you want to learn.
Taking continuing education classes at a community college may be cheaper than Rosetta Stone, and enables you to interact with other students learning the same language. Scholarships and grants may also be available to pay for your classes at community college or a local university.
Befriend a native speaker of the language you want to learn, and exchange language lessons. If English is a new language to your friend, she may be eager to exchange language lessons.
If your community has a large international community of immigrants or refugees, cultural centers serving those populations may offer ESL (English as a Second Language) courses. You may also find such courses at community colleges. Often teachers are in need of native English speakers to assist with large classes, and are open to volunteers.
Find international countries that speak the language you want to learn and apply for employment opportunities in those countries. You can immerse yourself in the culture while earning money. This is a great way to learn a language if you have a professional skill that's in demand, as some companies will pay for your language lessons so that you can be more productive.
There are numerous sites that offer free language lessons online, and other sites where you can download lessons onto your iPod or MP3 player for free or for a nominal fee. Social networking sites such as My Happy Planet allow language lovers to interact with and learn from one another. (See Resources.)